Sounds like so much work lol but I shall try out some of these methods, thanks.

Actually it isn't. If I was doing the whole slide I would do a a quick sanding, a coat of spray primer, and them 1-2 coats of the over-coat. Let it dry for a week and done. The only PITA is the waiting.

For my HK45 here's the estimated work

Scape off (gently) the white paint - 2 minutes

Birchwood Casey - I applied it and wasn't satisfied so you can skip this step

Mask of the area to paint with masking tape - 30 seconds

One light coat of Krylon Ultra Flat Black Camo - 3 minutes including shaking the can

After it sets, about,8hrs , I simply rub the finish a bit...but that's me, you don't need to.